Inferring the evolutionary relationships among organisms phylogeny reconstruction Lectures 11 12 Systematics a The discipline within biology that is concerned with b c Organizing and naming taxa classification d Study that establishes rules of classification taxonomy e Categories vary with our goals music genres over the years Schools of Biological classification a Phenetics i Classifies species based on overall similarity ii Not concerned with phylogeny iii Earliest approach but now uncommon b Cladistics i Classifies species based on phylogeny only ii Developed in the 1960s and now dominant c Evolutionary systematics i Classifies based partially on phylogeny ii Recognizes grades and clades I II III Linnaeus Hierarchical Classification a Kingdom Animalia b Class vertebrata c Order primates d Genus homo binomial nomenclature e Species sapiens binomial nomenclature f Linnaeus system is a collection of nested relationships As you move up the hierarchy you form more and more inclusive groups g Placental mammals i Carnivores cats and dogs ii Primates monkeys and lemurs h Marsupials i Possums ii Macropods kangaroos and wallabies i Linnaeus s groups were based on his judgment of similarity and were thought to reflect basic plans in the mind of God i For example Mammals were thought to be based on a general plan that has several features including hair and nursing the young j Linnaeus Classification scheme was phenetic based on overall similarity i It was not concerned with evolutionary relationships IV Taxonomy of the domestic dog domestic cat and a macaque a Binomial nomenclature each species scientific name contains both the genus and species name When written you write the binomen in italics Kingdom Phylum Class Order Family Genus Species Human Classification Dog Animalia Chordate Mammalia Carnivore Canididae Canis Lupus V Cat Animalia Chordate Mammalia Carnivore Felidae Felis Sylvestris Crab eating macaque Animalia Chordate Mammalia Primates Cercopithecidae Macaca Fascicularis a Kingdom Animalia b Phylum Chordata c Class Mamallia d Order Primate e Family Hominidae f Genus Homo g Species sapiens Before Darwin categories of living things were based only on similarity a Carnivores felids lions wild cats cheetahs canids wolves b Darwin explained such similarities in a very different way they were inherited from a VI common ancestor c Today our classification system reflects evolutionary relationships VII What information about organisms do we want to organize a Traits b Phylogeny Clade an ancestral species and all of its descendent species are nested within larger clades a The species in a clade share traits because VIII i Trait evolves in a lineage ii Trait persists in descendants iii All taxa in a clade exhibit trait b Shared traits suggest common ancestry i Today we use the hierarchical ranks created by Linnaeus but only give names to clades ii Clades are lineages so another name for a clade is monophyletic group iii Our job is to infer membership in a monophyletic group c Paraphyletic grouping an ancestral species and some of its descendants a group of species but not including the ancestor d Homology retained in descendants feature evolves here e Analogy similar features evolve twice Homoplasy Convergent evolution a Homologous traits i Shared ancestral symplesiomorphy IX 1 Not useful for phylogeny reconstruction 2 Symplesiomorphy a trait that is found in the last common ancestor of some specified group of taxa and that is expect to be in that ancestor s descendants shared ancestral trait 3 Not informative about relationships in in group because all taxa in the group should have it ii Shared derived synapomorphy 1 Only type used for phylogeny reconstruction 2 Synapomorphy a trait that has changed from the condition seen in the last common ancestor and which is shared among some of its descendants shared derived trait 3 Only trait type that is informative about relationships within the in group because only some taxa will share it b Analogous traits i Convergent trait Homoplasy 1 Mislead phylogeny reconstruction c A cladogram is not a phylogeny d Autapomorphy a trait that has changed from the condition seen in the last common ancestor and which is not shared among some of its descendants uniquely derived trait i Not informative about relationships because only one taxon has it e Ancestral trait and derived trait are relative terms i The placenta is a synapomorphy relative to the opossum ii The placenta is a symplesiomorphy relative to the wolf f Homoplasy i The prehensile tail evolves twice in a clade ii That trait is called a homoplasy iii Homoplasies are misleading about evolutionary relationships because they suggest incorrectly that taxa are closely related g Different kind of traits h And different ways of grouping taxa i Monophyletic paraphyletic polyphyletic i Synapomorphies symplesiomorphies autapomorphies Homoplasies X So how do we classify organisms i Evolutionary Systematics a Paraphyletic groups do not contain all descendants of a common ancestor b Distribution of living non human primates i Part of south America lower half of Africa and Europe c Body size very large range i Mouse lemur 3 5 ounces ii Male gorilla 400 pounds d Other distinctions habitats locomotion diet social organization e Primate features i Grasping hands and feet all have a nail on their big toe hallux rather than a claw Most have nails on all of their digits Primate hands are exceptionally dexterous ii Enhanced vision eyes rotate toward the front iii Postorbital bar iv Reduced sense of smell olfaction v Large complex brains vi The arboreal hypothesis primate features are adaptation for life in the trees Sir Wilfrid Le Gros Clark f Nonprimate mammals i Claws or hoofs on digits ii Divergent orbits g The comparative method i Method used to test hypothesis about adaptation ii Looks for repeated associations h The visual predation hypothesis Matt Cartmill i Primates are adapted to catching insects while in the trees Lecture 13 14 XI Cladogram of living primate groups a Ancestral mammal traits No postorbital bar five digits claws divergent orbits small brain wet noses large snout tapetum lucidum multiple nipples bicornuate uterus unfused mandibular symphysis i Rhinarium wet nose split upper lip ii Tapetum lucidum a reflective layer in the eye that aids in night seeing b Derived primate traits grasping extremities nail on hallux convergent orbits divergent orbits postorbital bar larger brain i Derived